Computers are often connected to a variety of external devices. These devices may themselves be other computers, digital devices or analog devices. In all cases, the computer interface is designed to interact with the attached devices using proper voltage and current levels.
Some devices require that their computer interface provide them with power besides facilitating communications. Such a requirement increases the complexity of the computer interface circuitry and introduces many problems.
One particular problem with interface supplied power involves maximum voltage and current supply capabilities. For example, a computer may be interfaced with a device having voltage and/or current requirements beyond that which the computer can supply. This particular problem becomes more severe when a low power computer system is interfaced to a device requiring a high current or high voltage power supply.
More specifically, for example, PC Cards (which are also known as PCMCIA cards and IC cards) have very limited current handling abilities. PC Cards cannot draw a large supply current or voltage from the host to which they are connected. Thus, if connected to a device with other than minimal power supply requirements, a PC Card cannot directly act as the power supply therefor. Interfacing PC Cards to such devices is thus problematic. Furthermore, even if a technique for supplying power to the interfaced device is somehow implemented, other issues such as power sequencing are raised.
The present invention is directed toward solutions to the above noted problems.